Anthelmintic Classes Research Articles

Equine Anthelmintic Resistance: Horse Owner and Yard Manager Perception of the Barriers Affecting Strategic Control Measures in England.

Simple SummaryEquine anthelmintic resistance poses a threat to the health and welfare of horses worldwide. With no new imminent anthelmintic classes, it is vital to decrease resistance rate and preserve available classes. Traditional indiscriminate anthelmintic use is not synonymous with a strategic control ideology; however, many continue to implement outdated practices. In comparison to livestock farmers, there have been few social science studies examining the behaviours of horse owners. This study aimed to understand the perceived barriers faced by horse owners and yard managers to adopting a strategic approach to helminth control, and to explore their experiences. Semi-structured interviews permitted the exploration of the stakeholders’ beliefs, opinions, experiences, attitudes, and behaviours. Personal resources, internal influences, and external influences were identified by participants as the barriers to adoption of strategic controls. Two further themes impacting effective implementation of strategic controls emerged surrounding helminth information and source, as well as accurate dosing. Challenges associated with anthelmintic administration and bodyweight estimation suggest that inaccurate dosing is prevalent. Industry wide implementation of a single ‘best practice’ could support prescriber decision-making to encourage uptake of effective strategic helminth controls. The barriers identified in this study could help influence guidance given to horse owners through a better understanding of their beliefs and behaviours.Equine anthelmintic resistance poses a threat to the health and welfare of horses worldwide. With no new imminent anthelmintic classes, it is vital to decrease the resistance rate and preserve available classes. Traditional indiscriminate anthelmintic use is not synonymous with a strategic control ideology; however, many continue to implement outdated practices. In comparison to livestock farmers, there have been few social science studies examining horse owner behaviours. This study aimed to understand the perceived barriers faced by horse owners and yard managers to adopting a strategic approach to helminth control, and to explore their experiences. Semi-structured interviews permitted the exploration of the stakeholders’ beliefs, opinions, experiences, attitudes, and behaviours. Personal resources, internal influences, and external influences were identified by participants as the barriers to adoption of strategic controls. Two further themes impacting effective implementation of strategic controls emerged surrounding helminth information and source, as well as accurate dosing. Challenges associated with anthelmintic administration and bodyweight estimation suggest that inaccurate dosing is prevalent. Industry-wide implementation of a single ‘best practice’ could support prescriber decision-making to encourage uptake of effective strategic helminth controls. The barriers identified in this study could help influence guidance given to horse owners through a better understanding of their beliefs and behaviours.

Genomic landscape of drug response reveals mediators of anthelmintic resistance.

SummaryLike other pathogens, parasitic helminths can rapidly evolve resistance to drug treatment. Understanding the genetic basis of anthelmintic drug resistance in parasitic nematodes is key to tracking its spread and improving the efficacy and sustainability of parasite control. Here, we use an in vivo genetic cross between drug-susceptible and multi-drug-resistant strains of Haemonchus contortus in a natural host-parasite system to simultaneously map resistance loci for the three major classes of anthelmintics. This approach identifies new alleles for resistance to benzimidazoles and levamisole and implicates the transcription factor cky-1 in ivermectin resistance. This gene is within a locus under selection in ivermectin-resistant populations worldwide; expression analyses and functional validation using knockdown experiments support that cky-1 is associated with ivermectin survival. Our work demonstrates the feasibility of high-resolution forward genetics in a parasitic nematode and identifies variants for the development of molecular diagnostics to combat drug resistance in the field.

Potential of Anthelmintic Herbal Drugs against Gastrointestinal Nematodes in Farm Animals: A Review

Gastrointestinal (GI) nematode infections are one of the most prevalent and significant problems in livestock worldwide. This study aimed to review the potential of anthelmintic herbal drugs against gastrointestinal nematodes in farm animals. Anthelmintic drugs are the most common method of controlling GI nematodes since they are simple, cheap, and provide therapeutic and prophylactic protection. However, the problem has become complicated due to the emergence of resistance to anthelmintic drugs because anthelmintic drugs are used indiscriminately to treat parasitic diseases. Anthelmintic resistance in GI nematodes of ruminants is a global problem. Many domestic animals possess multi-class resistance to all classes of anthelmintics. Synthetic anthelmintics could be unsafe as they can cause side effects and toxicity. Therefore, plants are used to develop and discover novel substances acting as anthelmintics. Herbal drugs have become increasingly popular because of their fewer side effects in recent years. Consequently, the demand for herbal formulations of anthelmintic drugs is increasing. The development of instrumental analysis accelerates the preparation of phytochemical constituents and their standardization, and this field is becoming critical for research.

Anthelmintic resistance of gastrointestinal nematodes in goats: A systematic review and meta-analysis

ObjectiveTo review anthelmintic resistance globally in goats including the effect of location, mode of application and dosage on anthelmintic efficacy (assessed using Faecal Egg Count Reduction). Specifically, resistance of the three major classes of anthelmintics – Benzimidazole and Probenzimidazole (BP); Anti-cholinergics (AC); and Macrocyclic Lactone (ML) was investigated. Design/procedureA PRISMA Framework was followed in order to conduct a thorough assessment of the literature on anthelmintic resistance in goats. A single factor ANOVA test was conducted in Microsoft Excel (2009) to test for the significance of the effect of location, mode of application and dosage on resistance. Three meta-analyses were also conducted in Microsoft Excel (2009) to quantify global resistance levels of the three major anthelmintic classes. ResultsOf the 461 publications screened, 105 studies were included in the systematic review and 101 studies were included in the meta-analyses. Anthelmintic class as well as anthelmintic active principle selection in the BP and ML classes did have a significant effect on resistance (p < 0.05). Combination treatment groups had a lower amount of resistance than groups where anthelmintic classes were used alone. Mode of application of the treatment had a significant effect on resistance (p < 0.05), whilst the correlation of dosage with efficacy was low (r < 0.1). The effect of location (by continent) also had a significant influence on resistance for the AC anthelmintic class (p < 0.05). All GIN species assessed with the exception of Chabertia spp. exhibited anthelmintic resistance. ConclusionsAnthelmintic resistance is a substantial global issue in the goat industry. More research needs to be conducted into anthelmintic resistance in regard to effective ways to use anthelmintics and minimise resistance.

In vitro evaluation of fitness parameters for isolates of Teladorsagia circumcincta resistant and susceptible to multiple anthelmintic classes

Anthelmintic resistance (AR) is an ever increasing problem for the sheep industry. Several studies worldwide have investigated reversing the trend of increasing AR and documented evidence for reversion toward susceptibility has been found. The hypothesis that resistance mutations compromise parasite fitness was drawn from this evidence.The aim of this study was to assess whether there were measurable differences in the fitness of Teladorsagia circumcincta isolates depending on their AR status. Four isolates were selected for the trial based on their known resistance status; D and M were multi-drug resistant, and T and W were susceptible to the benzimidazole, levamisole, and macrocyclic lactone anthelmintic classes. A secondary aim was to develop a series of in vitro bioassays for assessing fitness characteristics of parasites.The in vitro assays included; the cold stress test measured the number of third stage larvae (L3) developing from eggs stored at 4 °C for different lengths of time. Larval aging measured the locomotory activity of L3 after storage at 30 °C for different lengths of time. The exsheathment assay measured the exsheathment percentage of L3. Larval Length used length as a proxy for fecundity. The egg hatch assay evaluated egg hatch rate in water at room temperature.All isolates exhibited a decrease in the number of L3 recovered after storage of eggs at 4 °C (p < 0.001). Storage of L3 at 30 °C significantly influenced the ability of L3 to migrate through a 20 µm sieve (p < 0.001), however, there were no differences between isolates (p > 0.05). Exsheathment rate was higher for isolate D in comparison to isolates M and W, and for isolate T compared to isolate W. Isolate W was significantly longer than all other isolates (p < 0.05), whilst isolate M was significantly longer than isolate D (p < 0.05). No significant differences were found between isolates in egg hatch (p > 0.05).Overall, the results do not support differences in fitness associated with anthelmintic resistance status, even though differences were seen between the isolates for some assays. This suggests there is considerable variation in fitness parameters between isolates, making it difficult to determine whether resistance genotypes come with lower fitness.

Allele specific PCR for a major marker of levamisole resistance in Haemonchus contortus

Haemonchus contortus is a haematophagous parasitic nematode that infects small ruminants and causes significant animal health concerns and economic losses within the livestock industry on a global scale. Treatment primarily depends on broad-spectrum anthelmintics, however, resistance is established or rapidly emerging against all major drug classes. Levamisole (LEV) remains an important treatment option for parasite control, as resistance to LEV is less prevalent than to members of other major classes of anthelmintics. LEV is an acetylcholine receptor (AChR) agonist that, when bound, results in paralysis of the worm. Numerous studies implicated the AChR sub-unit, ACR-8, in LEV sensitivity and in particular, the presence of a truncated acr-8 transcript or a deletion in the acr-8 locus in some resistant isolates. Recently, a single non-synonymous SNP in acr-8 conferring a serine-to-threonine substitution (S168T) was identified that was strongly associated with LEV resistance. Here, we investigate the role of genetic variation at the acr-8 locus in a controlled genetic cross between the LEV susceptible MHco3(ISE) and LEV resistant MHco18(UGA2004) isolates of H. contortus. Using single worm PCR assays, we found that the presence of S168T was strongly associated with LEV resistance in the parental isolates and F3 progeny of the genetic cross surviving LEV treatment. We developed and optimised an allele-specific PCR assay for the detection of S168T and validated the assay using laboratory isolates and field samples that were phenotyped for LEV resistance. In the LEV-resistant field population, a high proportion (>75%) of L3 encoded the S168T variant, whereas the variant was absent in the susceptible isolates studied. These data further support the potential role of acr-8 S168T in LEV resistance, with the allele-specific PCR providing an important step towards establishing a sensitive molecular diagnostic test for LEV resistance.

Interactions of Caenorhabditis elegans β-tubulins with the microtubule inhibitor and anthelmintic drug albendazole.

Parasitic nematodes are major human and agricultural pests, and benzimidazoles are amongst the most important broad-spectrum anthelmintic drug class used for their control. Benzimidazole resistance is now widespread in many species of parasitic nematodes in livestock globally and an emerging concern for the sustainable control of human soil-transmitted helminths. β-tubulin is the major benzimidazole target, although other genes may influence resistance. Among the 6 Caenorhabditis elegans β-tubulin genes, loss of ben-1 causes resistance without other apparent defects. Here, we explored the genetics of C. elegans β-tubulin genes in relation to the response to the benzimidazole derivative albendazole. The most highly expressed β-tubulin isotypes, encoded by tbb-1 and tbb-2, were known to be redundant with each other for viability, and their products are predicted not to bind benzimidazoles. We found that tbb-2 mutants, and to a lesser extent tbb-1 mutants, were hypersensitive to albendazole. The double mutant tbb-2 ben-1 is uncoordinated and short, resembling the wild type exposed to albendazole, but the tbb-1 ben-1 double mutant did not show the same phenotypes. These results suggest that tbb-2 is a modifier of albendazole sensitivity. To better understand how BEN-1 mutates to cause benzimidazole resistance, we isolated mutants resistant to albendazole and found that 15 of 16 mutations occurred in the ben-1 coding region. Mutations ranged from likely nulls to hypomorphs, and several corresponded to residues that cause resistance in other organisms. Null alleles of ben-1 are albendazole-resistant and BEN-1 shows high sequence identity with tubulins from other organisms, suggesting that many amino acid changes could cause resistance. However, our results suggest that missense mutations conferring resistance are not evenly distributed across all possible conserved sites. Independent of their roles in benzimidazole resistance, tbb-1 and tbb-2 may have specialized functions as null mutants of tbb-1 or tbb-2 were cold or heat sensitive, respectively.

Effectiveness of Anthelmintic Treatments in Small Ruminants in Germany.

Simple SummaryParasitic worms are a major threat to the health and production of sheep and goats worldwide, particularly because many worms have become resistant to commonly applied drugs. This problem is well known around the world, but the situation is currently not well studied in Germany. This study was therefore performed to evaluate the effectiveness of treatments against infection with gastrointestinal nematodes. Faecal samples from animal groups were examined before and after treatment, the worm eggs in the feaces were counted, and the reduction in egg excretion following treatment was calculated. Eggs of Haemonchus contortus (barber’s pole worm) were stained to differentiate them from other gastrointestinal nematodes. Treatments were chosen and carried out by farmers together with their local veterinarian. Additional information was collected by questionnaires to check if the treatments were performed correctly. Reduced effectiveness was observed for all available drugs, but some showed better treatment success than others. The barber’s pole worm frequently survived treatments by most products. The high percentage of treatment failures is highly concerning, and it is necessary to develop and/or apply alternative methods of worm control to prevent the deterioration of this situation.Widespread anthelmintic resistance is a concern for small ruminant health and production worldwide. The current situation regarding anthelmintic efficacy is, however, not very well studied in Germany. Thus, a nationwide field study was undertaken to assess the effectiveness of 253 treatments performed in 223 small ruminant flocks by faecal egg count reduction test (FECRT) using pooled samples and a modified McMaster method. The percentage of Haemonchus contortus and non-Haemonchus eggs was determined by fluorescence microscopy following peanut agglutinin–fluorescein isothiocyanate staining. Treatments were chosen and performed by farmers together with their local veterinarian, and potentially confounding factors for FECRT results were addressed as far as possible by rigorous inclusion criteria. Reduced effectiveness was observed for treatments with all examined anthelmintic classes, but treatments with benzimidazoles and moxidectin showed significantly poorer results than monepantel, a closantel and mebendazole combination, and levamisole. Low case numbers precluded reliable assessment of avermectins. Unsuccessful treatments were frequently associated with the survival of H. contortus, but this was also observed for non-Haemonchus genera. The results are highly concerning, and sustainable approaches to parasite control are urgently needed to prevent further deterioration of this situation.

Assessing the Anthelmintic Candidates BLK127 and HBK4 for Their Efficacy on Haemonchus contortus Adults and Eggs, and Their Hepatotoxicity and Biotransformation.

As a widely distributed parasitic nematode of ruminants, Haemonchus contortus has become resistant to most anthelmintic classes, there has been a major demand for new compounds against H. contortus and related nematodes. Recent phenotypic screening has revealed two compounds, designated as BLK127 and HBK4, that are active against H. contortus larvae. The present study was designed to assess the activity of these compounds against H. contortus eggs and adults, hepatotoxicity in rats and sheep, as well as biotransformation in H. contortus adults and the ovine liver. Both compounds exhibited no inhibitory effect on the hatching of eggs. The benzyloxy amide BLK127 significantly decreased the viability of adults in sensitive and resistant strains of H. contortus and showed no hepatotoxic effect, even at the highest concentration tested (100 µM). In contrast, HBK4 had no impact on the viability of H. contortus adults and exhibited significant hepatotoxicity. Based on these findings, HBK4 was excluded from further studies, while BLK127 seems to be a potential candidate for a new anthelmintic. Consequently, biotransformation of BLK127 was tested in H. contortus adults and the ovine liver. In H. contortus, several metabolites formed via hydroxylation, hydrolysis and glycosidation were identified, but the extent of biotransformation was low, and the total quantity of the metabolites formed did not differ significantly between the sensitive and resistant strains. In contrast, ovine liver cells metabolized BLK127 more extensively with a glycine conjugate of 4-(pentyloxy)benzoic acid as the main BLK127 metabolite.

Increasing resistance to multiple anthelmintic classes in gastrointestinal nematodes on sheep farms in southwest England.

BackgroundAnthelmintic resistance (AR) in gastrointestinal nematodes (GIN) is increasing globally, and farmers are encouraged to adopt sustainable control measures. Haemonchus contortus is increasingly reported in the UK, potentially complicating effective GIN control.MethodsFaecal egg count reduction tests (FECRT) were conducted on 13 farms in north Devon, England, UK in 2016. Relative abundance of H. contortus was quantified using peanut agglutinin staining and used to estimate faecal egg count reduction percentages (FECR%) using the eggCounts R package.ResultsOn average, farms had GIN resistance to three anthelmintic classes. No farms had susceptibility to all anthelmintics tested. AR was more prevalent in 2016 than on the same farms in 2013. H. contortus was present on 85% of the farms tested and comprised on average 6% (0%–52%) of GIN eggs before treatment. Resistance or suspected resistance to all anthelmintics tested was observed in this species on different farms.ConclusionThe results demonstrate diversity of AR profiles on farms, apparent progression of AR within a 3‐year period, and challenges detecting AR in mixed‐species infections. Where possible, interpretation of mixed‐species FECRT should take into account the relative abundance of species pre‐ and post‐treatment to identify pragmatic treatment options targeting individual genera.

Pharmacotherapy of gastrointestinal strongylosis of small ruminants: An update

Gastrointestinal strongylosis, which causes deadly seasonal diarrhea in small ruminants, is a major threat to the livestock population in sub-Saharan Africa. Moreover, livestock is a central component of food security. In addition to this threat, there is a poor veterinary coverage due to the increasing lack of effective anthelmintic drugs against strongyles because of the emergence and proliferation of chemo resistant strains. In this context, and given that the use of a vaccine is not widespread, the establishment of the therapeutic arsenal available to veterinarians to control strongyles will contribute to the food and economic security of rural populations. This review outlines the main pharmacochemical classes of anthelmintics used in the management of strongylosis of small ruminants.

Schistosoma mansoni α-N-acetylgalactosaminidase (SmNAGAL) regulates coordinated parasite movement and egg production.

α-galactosidase (α-GAL) and α-N-acetylgalactosaminidase (α-NAGAL) are two glycosyl hydrolases responsible for maintaining cellular homeostasis by regulating glycan substrates on proteins and lipids. Mutations in the human genes encoding either enzyme lead to neurological and neuromuscular impairments seen in both Fabry- and Schindler/Kanzaki- diseases. Here, we investigate whether the parasitic blood fluke Schistosoma mansoni, responsible for the neglected tropical disease schistosomiasis, also contains functionally important α-GAL and α-NAGAL proteins. As infection, parasite maturation and host interactions are all governed by carefully-regulated glycosylation processes, inhibiting S. mansoni's α-GAL and α-NAGAL activities could lead to the development of novel chemotherapeutics. Sequence and phylogenetic analyses of putative α-GAL/α-NAGAL protein types showed Smp_089290 to be the only S. mansoni protein to contain the functional amino acid residues necessary for α-GAL/α-NAGAL substrate cleavage. Both α-GAL and α-NAGAL enzymatic activities were higher in females compared to males (p<0.05; α-NAGAL > α-GAL), which was consistent with smp_089290's female biased expression. Spatial localisation of smp_089290 revealed accumulation in parenchymal cells, neuronal cells, and the vitellaria and mature vitellocytes of the adult schistosome. siRNA-mediated knockdown (>90%) of smp_089290 in adult worms significantly inhibited α-NAGAL activity when compared to control worms (siLuc treated males, p<0.01; siLuc treated females, p<0.05). No significant reductions in α-GAL activities were observed in the same extracts. Despite this, decreases in α-NAGAL activities correlated with a significant inhibition in adult worm motility as well as in egg production. Programmed CRISPR/Cas9 editing of smp_089290 in adult worms confirmed the egg reduction phenotype. Based on these results, Smp_089290 was determined to act predominantly as an α-NAGAL (hereafter termed SmNAGAL) in schistosome parasites where it participates in coordinating movement and oviposition processes. Further characterisation of SmNAGAL and other functionally important glycosyl hydrolases may lead to the development of a novel anthelmintic class of compounds.

Benzimidazole resistant Haemonchus contortus in a wildlife park.

Anthelmintic resistance (AR) of ruminant gastrointestinal nematodes (GINs) constitutes a major problem worldwide. Among GINs, the abomasal blood-feeding parasite Haemonchus contortus is particularly pathogenic and may show resistance against all major anthelmintic substance classes. In the present study, the death of a 1,5 year-old European bison (Bison bonasus) from a German wildlife park due to haemonchosis despite frequent anthelmintic treatment of the herd with fenbendazole as well as doramectin prompted an investigation regarding AR. Pooled faecal samples were collected from four different bison groups as well as from mouflons (Ovis orientalis), elk (Alces alces), reindeer (Rangifer tarandus), sika deer (Cervus nippon), Persian fallow deer (Dama mesopotamica) and red deer (Cervus elaphus) housed by the wildlife park. After coproscopical examination, faecal larval cultures were established. Haemonchus contortus-positive larval cultures were further examined for genetic polymorphisms associated with benzimidazole resistance at codons 167 and 200 of the β-tubulin isotype 1 gene by real-time pyrosequencing. Infections with H. contortus were detected in all four bison groups, as well as in mouflons. In five samples, representing two bison groups and the mouflons, the frequency of the resistance-associated single-nucleotide polymorphism (SNP) at codon 200 was 100%. In contrast, resistance-associated SNPs were not detected at codon 167. In addition, faecal egg counts from two bison before and 14 days after parenteral doramectin treatment indicated possible macrocyclic lactone resistance. Detection of anthelmintic resistant nematodes in these animals was especially concerning in the light of planned reintroduction into the wild. As helminth control in zoological gardens and wildlife parks relies mostly on anthelmintic treatment due to restricted possibilities regarding management practices such as rotational grazing, care should be taken to avoid underdosing or unnecessary frequent treatments facilitating the development of AR.

The Caenorhabditis elegans DEG-3/DES-2 Channel Is a Betaine-Gated Receptor Insensitive to Monepantel.

Natural plant compounds, such as betaine, are described to have nematocidal properties. Betaine also acts as a neurotransmitter in the free-living model nematode Caenorhabditis elegans, where it is required for normal motility. Worm motility is mediated by nicotinic acetylcholine receptors (nAChRs), including subunits from the nematode-specific DEG-3 group. Not all types of nAChRs in this group are associated with motility, and one of these is the DEG-3/DES-2 channel from C. elegans, which is involved in nociception and possibly chemotaxis. Interestingly, the activity of DEG-3/DES-2 channel from the parasitic nematode of ruminants, Haemonchus contortus, is modulated by monepantel and its sulfone metabolite, which belong to the amino-acetonitrile derivative anthelmintic drug class. Here, our aim was to advance the pharmacological knowledge of the DEG-3/DES-2 channel from C. elegans by functionally expressing the DEG-3/DES-2 channel in Xenopus laevis oocytes and using two-electrode voltage-clamp electrophysiology. We found that the DEG-3/DES-2 channel was more sensitive to betaine than ACh and choline, but insensitive to monepantel and monepantel sulfone when used as direct agonists and as allosteric modulators in co-application with betaine. These findings provide important insight into the pharmacology of DEG-3/DES-2 from C. elegans and highlight the pharmacological differences between non-parasitic and parasitic nematode species.

Evaluation of risk factors affecting strongylid egg shedding on Hungarian horse farms

In Hungary, equine parasite control is mostly based on traditional approaches involving rotational anthelmintic treatment at regular intervals. Almost no farms utilize fecal egg counts (FECs) on a regular basis to guide deworming treatments. This approach is certainly not sustainable and is the major factor responsible for the current high levels of anthelmintic resistance. The aims of this study were to statistically analyze risk factors associated with strongylid egg count magnitude and prevalence. Fecal samples and horse data (age, pasture history, stocking density, anthelmintic history) were collected from 216 horses on 13 farms in Pest county, Hungary, during the spring of 2020. FECs were determined by Mini-FLOTAC. Logistic regression models were used to evaluate the association of factors with pre-deworming strongylid egg counts. The data were highly overdispersed with approximately 22% (95% Confidence Interval: 17-28%) of the equids shedding 80% of the total strongylid egg output. Strongylid FECs were significantly associated with the age of equids and anthelmintic class used prior to the study. Equids younger than 5years of age had significantly higher FECs compared to equids in the 5-17-year age range (p=0.003) and compared to equids aged >17years (p<0.001). Equids treated regularly with benzimidazoles had significantly higher FECs than equids with no history of benzimidazole use (p=0.02). We found that FECs of horses kept at extremely high stocking density (>30 horses/ha) were significantly higher than those kept at low (1-2 horses/ha; p<0.001) or medium (3-10 horses/ha, p<0.001) stocking densities. The results demonstrate the value of FEC monitoring and indicate that the efficacy of benzimidazoles should be investigated in Hungary. Moreover our findings demonstrate that reducing stocking density should be considered in cases of high strongylid FECs.

Ethnoveterinary survey of plants used for the control of gastrointestinal nematodes in sheep at three agro-ecological zones in the Eastern Cape Province of South Africa

Background: With exception of the desert biome, all of South Africa’s biomes occur in the Eastern Cape. The province is known to have high numbers of livestock that are mostly found in communal farming areas. Multi-drug resistance of gastrointestinal nematodes against major classes of conventional anthelmintics and the high cost of synthetic drugs calls for an urgent search for different control strategies of nematodes.Aim: A survey was conducted to identify and document plant species used to control gastrointestinal nematodes of livestock in Ciko, Goso and Upper Ngqumeya communities in the Eastern Cape Province.Setting: The study included filed observations and transect walks, as well as a standardized questionnaire given to 48 sheep farmers.Methodology: Forty-eight livestock farmers including men and women of mixed ages were interviewed. The information was obtained through the use of a structured questionnaire, field observations and transect walks. Data generated were analysed using descriptive statistics with frequency of citation (FC) and relative frequency of citation (RFC) as quantitative.Results: A total of 11 plant species from different genera were reportedly available and used to control gastrointestinal nematodes. Aloe ferox (0.67) and Zanthoxylum capense (0.44) had the highest values of RFC followed by Strychnos henningsii (0.23) and Elaphantorhhiza elephantine (0.21) and were widely known by the people of the study areas. The three most frequently used plant parts were leaves, roots and bark accounting for about 36.4%, 27.3% and 27.3%, respectively. The ethnoveterinary medicines were prepared in the form of decoctions and infusions. Oral administration of the concoctions was the only route of administration. The major constraints of sheep production as perceived by the farmers were prevalence of internal (36%) and external parasites (18.1%). All medicinal plants used were native and collected from the wild. The most dominant life forms were trees (45.4%), followed by herbs (36.4%) and shrubs (18.2%). Homestead expansion was ranked as the major threat (26%) to medicinal plants followed by firewood (21%). In-situ (protection through rangers) was the most frequently mentioned (67%) conservation practice used by farmers to protect the loss of medicinal plants followed by ex-situ (33%).Conclusion: In the light of data gathered on the surveyed plants, it appeared the plants play a role in the healthcare of sheep in rural communities. Further studies are required to analyse the plants for their chemical composition and biological properties.

Prevalence of anthelmintic resistant cyathostomins in Prince Edward Island, Canada.

Cyathostomins are the most common parasites of adult horses worldwide. Currently, the three classes of anthelmintics used to treat cyathostomin infections includes benzimidazoles, pyrimidines and macrocyclic lactones. However, due to widespread overuse, cyathostomins have developed varying degrees of resistance to all classes of anthelmintics. Fecal egg count reduction tests (FECRT) are currently used to determine the presence of anthelmintic resistance (AR), while egg reappearance periods (ERP) are used to investigate early macrocyclic lactone resistance. The objective of this study was to investigate the prevalence of cyathostomin pyrantel pamoate and ivermectin resistance, and to determine ERP at Prince Edward Island (PEI), Canada horse farms. In addition, fecal cultures and larval identification were performed to evaluate the prevalence of small and large strongyle egg shedding in PEI. Fecal egg counts (FEC) were performed on 270 horses on 14 horse farms across PEI. Horses with≥ 200 eggs per gram (EPG) met the inclusion criteria and were enrolled in the study (n=101). The median (range) horses per farm was 7.5 (4-11) and 6.0 (4-8) for pyrantel pamoate and ivermectin groups, respectively. Horses were initially treated with 6.6mg/kg of pyrantel pamoate orally (n=101). Fecal egg counts were conducted every two weeks for 8weeks post treatment. Once individual FEC were ≥ 200 EPG, horses were dewormed with 0.2mg/kg of ivermectin orally (n=80), and FEC were performed every 2-3weeks for seven weeks. In this study the ERP was defined as the week the mean FECR were 10% below the initial mean two-week post treatment FECR. Fecal egg count reduction tests and ERP were used to evaluate the efficacy of each anthelmintic. Fecal culture was performed to confirm the shedding of cyathostomin eggs. Fecal egg count reduction tests detected pyrantel pamoate resistance on 5/14 farms. No signs of ivermectin AR were detected, while reappearance of eggs occurred at 4-6weeks and 7-9weeks for pyrantel pamoate and ivermectin, respectively. Fecal culture detected large strongyles on 5/14 farms, which accounted for 0.3% of strongyle type eggs cultured. The prevalence of Strongylus vulgaris among individual horses in this study was 2.8% and was detected on 2/14 farms. These findings will allow us to educate owners and veterinarians on appropriate anthelmintic protocols in PEI and can be used as a baseline for continued monitoring of ERP and anthelmintic resistance in this region.

Advances in diagnosis and control of anthelmintic resistant gastrointestinal helminths infecting ruminants.

Infection with gastrointestinal helminths is widely spread among ruminant causing severe losses and adversely affects the livestock husbandry. Synthetic chemotherapeutics have been utilized throughout years, as a means of combating helminthiasis. Anthelmintic resistance (AR) has a serious concern on livestock industry which, mainly arises as outcome of misuse, improper dosing and frequent utilization of the synthetic drugs.Various gastrointestinal helminths have the capability to survive the therapeutic dose of anthelmintics and become resistant to the major anthelmintic classes. Early diagnosis might delay or reduce the risk of AR. Conventional phenotyping methods were commonly used for detection of anthelmintic resistant helminths, but appeared to lack of sensitivity, especially when the frequency of resistant allele is very low. Several molecular assays were carried out to detect the AR with greater accuracy. Sustainable effective preventive and control measures for gastrointestinal helminths infection remain the corner stone to overcome AR. Rational use of anthelmintics with keeping unexposed proportion of worm populations, could have the potentiality to maintain and prolong the efficacy of anthelmintics. Several alternative anthelmintic treatments might offer valuable solutions either alone or adjunct to synthetic drugs to dilute the spread of resistance alleles among the helminths population. This article reviews current status of various diagnostic methods and control measures for anthelmintic resistant gastrointestinal helminths infecting ruminants and tries to present a practical protocol to avoid or delay the development of AR.

Newly identified parasitic nematode beta-tubulin alleles confer resistance to benzimidazoles

Infections by parasitic nematodes cause large health and economic burdens worldwide. We use anthelmintic drugs to reduce these infections. However, resistance to anthelmintic drugs is extremely common and increasing worldwide. It is essential to understand the mechanisms of resistance to slow its spread. Recently, four new parasitic nematode beta-tubulin alleles have been identified in benzimidazole (BZ) resistant parasite populations: E198I, E198K, E198T, and E198stop. These alleles have not been tested for the ability to confer resistance or for any effects that they might have on organismal fitness. We introduced these four new alleles into the sensitive C. elegans laboratory-adapted N2 strain and exposed these genome-edited strains to both albendazole and fenbendazole. We found that all four alleles conferred resistance to both BZ drugs. Additionally, we tested for fitness consequences in both control and albendazole conditions over seven generations in competitive fitness assays. We found that none of the edited alleles had deleterious effects on fitness in control conditions and that all four alleles conferred strong and equivalent fitness benefits in BZ drug conditions. Because it is unknown if previously validated alleles confer a dominant or recessive BZ resistance phenotype, we tested the phenotypes caused by five of these alleles and found that none of them conferred a dominant BZ resistance phenotype. Accurate measurements of resistance, fitness effects, and dominance caused by the resistance alleles allow for the generation of better models of population dynamics and facilitate control practices that maximize the efficacy of this critical anthelmintic drug class.

Natural Products Are a Promising Source for Anthelmintic Drug Discovery.

Parasitic nematodes infect almost all forms of life. In the human context, parasites are one of the major causative factors for physical and intellectual growth retardation in the developing world. In the agricultural setting, parasites have a great economic impact through a reduction in livestock performance or control cost. The main method of controlling these devastating conditions is the use of anthelmintic drugs. Unfortunately, there are only a few anthelmintic drug classes available in the market and significant resistance has developed in most of the parasitic species of livestock. Therefore, development of new anthelmintics with different modes of action is critical for sustainable parasitic control in the future. The drug development pipeline is broadly limited to two types of molecules, namely synthetic compounds and natural plant products. Compared to synthetic compounds, natural products are highly diverse, and many have historically proven valuable in folk medicine to treat various gastrointestinal ailments. This review focus on the use of traditional knowledge-based plant extracts in the development of new therapeutic leads, the approaches used as screening techniques, and common bottlenecks and opportunities in plant-based anthelmintic drug discovery.